Material handling implements of the type under consideration are well known. These off-highway implements embody a frame with a pair of lift arms pivotally connected to the frame. A material handling unit, such as a bucket, is pivotally connected to and between opposite ends of the respective lift arms. Lift actuators are connected between the frame of the implement and the lift arms for elevationally positioning the bucket relative to the frame of the implement. Tilt actuators are connected between the lift arms and the bucket for effecting pivotal fore-and-aft movement of the bucket to dump the contents thereof.
During normal operation, the lift arms are in a lowered position such that the bucket is positioned to have a lower edge or wall thereof generally flat with respect to the ground to facilitate filling the bucket. After the bucket is filled, it is tilted or rolled back with respect to the lift arms to maintain the contents within the bucket as it is raised to a position to enable dumping of the bucket or transfer the contents to some other location. As the lift arms are raised, it is necessary for the bucket to the pivoted with respect to the lift arms to maintain the bucket in a generally level position and prevent spilling of the contents.
Many implements having loader mechanisms attached thereto utilize a single handle control mechanism for both elevating the bucket and for dumping the bucket. During operation of the implement, however, it is not unusual for the operator to become confused and/or inadvertently move the single handle control in a wrong direction resulting in rolling movement of the bucket. Inappropriate rolling movements of the bucket when the lift arms are raised above the operator station can and often does result in the dumping of the materials onto the operator station of the implement.
Thus, there is a need and a desire for an anti-rollback mechanism which does not interfere with normal operation of the single handled control and yet automatically adjusts the position of the bucket relative to the lift arms as a function of the angular disposition of the lift arms relative to the frame of the implement.